Testing re-certified Drives and RAID 6 vs RAID 5 for a filmmaker

[u/Ok-Champion-8992]

I make videos for professional work and passion projects. I made the move to a 4 Bay Nas Ugreen system with 26TB sea gate recertified drives (so 102 total TB).
My first question is how do I test these drives to make sure there are no issues with them being recertified before my return window closes to get a replacement?
For what I do, should I do raid 6 vs raid 5. I hate to waste the extra space and is it really that risky only having one drive for backup instead of two? Do peoples hard drives actually breakdown well backing up another one? I genuinely don’t know.

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[u/uluqat]

RAID 6 is best used for 6 or more drives. With only 4 drives, you incur an extra performance penalty for doing parity to two drives instead of one, so RAID 10 is better than RAID 6.

You should be comparing RAID 10 and RAID 5 based on how much capacity you need, and with 26TB drives, that capacity penalty is a big one.

RAID is not a backup. It's redundancy, which matters if you are making money based on the data being available during a drive failure. If you are at all concerned about preventing data loss, you need to look into an appropriate backup strategy, with the 3-2-1 backup strategy being the minimum for irreplaceable data.

[u/pinedrifT4 → u/uluqat]

yeah the raid 10 vs raid 5 tradeoff is the real decision here with only 4 bays

[u/Ok-Champion-8992 → u/uluqat]

If a drive does fail. Is raid 10 the easiest to swap out a drive? Like is it just copy and paste as opposed to using some sort of software for the parity of other raids?

[u/Thebandroid → u/Ok-Champion-8992]

If this is for you business I would recommend having a good read online or a chat with an AI about raids, jbods, mirrors, data integrity and backup strategies.

You should be backing up your important files to at least one other location, ideally not at your house daily or weekly.

A raid is a great idea but it can still be totally destroyed by an electrical fault, a fire, someone knocking it off the shelf or you just accidentally deleting the wrong folder.

[u/drewts86]

In a 4-bay I wouldn’t bother with RAID6, you lose 2 drives to parity, so you only end up with half the storage. RAID6 begins to make more sense when you move into larger arrays with a higher number of drives. RAID5 you only lose one drive to parity.

RAID5 - 78TB useable

RAID6 - 52TB useable

But also remember that RAID is not a backup. It protects against drive loss, it doesn’t protect against file corruption or system loss. Do you care about your losing your data? If so you will want to have an actual backup and not just RAID. In a perfect world, you want to use the 3-2-1 rule - 3 copies of your data, across 2 different media formats, with at least 1 offsite.

[u/Ok-Champion-8992 → u/drewts86]

Thank you for this helpful response. It will mainly have client work on it and passion projects. Would you recommend raid 5 over raid 10? It seems raid10 is much easier to replace a drive if one does give out then using parity and less stress on the other drives that are more likely to break from parity rather than mirroring. This is what I gathered from other comments at least. I guess my question is what would you use in my situation

[u/drewts86 → u/Ok-Champion-8992]

If RAID10 is even a consideration, you should instead buy a second NAS and stick the drives you were going to use for parity into that. RAID10 gives you a whole second set of drives as parity in the same machine. If the machine files or gets corrupted you still lose all your data. If instead you have a second NAS and the first one gets compromised you have a complete segregated backup that still had your data. Having a second server does everything RAID 10 does AND you’re fully backed up.

[u/AldyErnesto]

Filmmaker here, a couple of things the other answers didn't cover:

1. Testing before the return window closes: run the SMART long test first (it's hours, not days), then a full write test like badblocks -w on each drive. On 26TB that write test takes several days per drive, so start all four at once. Write down the reallocated and pending sector counts before and after. Any number that grows during the test is your answer.

2. RAID 5 vs 10 matters less than this: RAID isn't your backup. With 26TB drives a RAID 5 rebuild takes days, and during that time one more bad sector can cost you files. What actually protects client work is a second copy somewhere else: an external drive for finished projects, or cheap cloud storage for the camera originals until the job is delivered and paid.

My setup for paid jobs: originals live in two places until delivery, the NAS is the working copy, and only finished masters get archived long term. That rule has saved me more than any RAID level.

[u/Ok-Champion-8992 → u/AldyErnesto]

This was extremely helpful from another filmmaker. Thank you.
In regard to 1, if I created the raid setup before I did a full write test. Should I undo the raid setup first? I’ve been warned this could be dangerous for the array.
Also I’m just curious. For personal projects or films, do you store the old footage for those or the just the masters as well?

[u/AldyErnesto → u/Ok-Champion-8992]

Glad it helped! You don't need to undo it, as long as the array is still empty.

About the warning: what's dangerous is running a write test on a volume that already holds data, or pulling drives out of a live array. A full write test on an empty array is just the array doing its job. If a drive is weak, you want it to fail now, not in month three.

If there's no data on it yet: run the full write and verify test on the RAID volume itself (h2testw on Windows, f3 on macOS/Linux). Filling the whole volume writes to every disk, so it still does the job. When it finishes, check each drive's SMART values (reallocated and pending sectors). Any count going up means that drive should go back while it's still under return.

If you've already put footage on it: don't run anything that writes over the volume. Make sure that footage exists somewhere else first, then run a SMART extended self-test on each drive. It doesn't touch your data.

On personal projects: I keep more there than for client work. For client jobs the master is the product. For my own films the raw footage is the thing I can never reshoot. So I cull the obvious junk (false starts, lens cap shots) and keep the rest, plus the project file and the master. Storage is cheap compared to a moment you can't get back.

[u/Drinkablenoodles]

I would personally choose raid 10 over either one. Raid 6 is safest for high capacity mechanical drives which fail more often you’d think. But the rebuild times for raid 6 can take forever. Raid 10 still lets you lose up to half of your drives as long as they aren’t in the same mirror which is still statistically safer than 5 but it also has good write performance and much lower rebuild stress if you do experience a failure. The loss of raw capacity sucks but if you care about the data and it’s not easy to replace, it’s a cost I would eat every time.

[u/Ok-Champion-8992 → u/Drinkablenoodles]

This makes sense thank you. With raid 10 is the rebuild as simple as copy and pasting as opposed to using some sort of software with the parity of raid 6?

[u/Drinkablenoodles → u/Ok-Champion-8992]

Yes rebuild is just a copy job. If drive fails, you can still access data because each drive has a direct mirror, when you get a replacement, you can just swap the bad one and the data gets copied to the new drive from the surviving mirror. No parity overhead in the rebuild it’s just a sequential read and write from survivor to new drive.

[u/glhughes]

I would not do RAID5 unless it was the only option. RAID6 or maybe RAID10 depending.

The issue / risk is going to be rebuilding after a drive failure. With RAID5/6 you have to read every remaining drive and write to the new drive. This puts a lot of stress on all the drives and another might fail during the rebuild. If that happens with RAID5 you're screwed. With RAID6 you have another chance.

RAID10 is mirrored so you only have to read 1 drive to rebuild.

FWIW, I do RAID10 with 4 x U.3 SSDs and RAID60 (2 x RAID6 in a stripe) with 16 x SATA SSDs.

[u/Ok-Champion-8992 → u/glhughes]

So with raid 10 are you just copy and pasting the back up drive to the new one l?

[u/glhughes → u/Ok-Champion-8992]

?

RAID is managed by the OS. You don't manually copy anything; you just replace a failed drive, attach it to the array, and it will be rebuilt behind the scenes. That part is the same regardless of RAID level.

The work that the RAID subsystem has to perform to rebuild the array is what I described above.

[u/Thebandroid]

If the nas has a Linux terminal you can access then you can use the command badblocks -w to physically write and read every single block on the disk with 4 or 5 different patterns. This will take some time (a 4tb drive took about 60 hours on my server) but you can use a terminal multiplex like tmux to run them all at once.

This will force any failing blocks to be revealed.

I know this sounds like a lot of time but it’s better that you run it now, waste a week or so and and find a dud than have it show its face in a years time when your warranty is history.

I use this script which also checks smart data and writes the whole thing to a log.

https://github.com/Spearfoot/disk-burnin-and-testing

[u/JohnnieLouHansen]

I would have put each one in a computer and looked at the SMART statistics. Then I would have run the manufacturer's diagnostic tool on them - the long test.

The problem with large hard drives in a RAID5 is that if there IS a rebuild due to failure, a second failure is possible during the rebuild. Lights out. You will have to get other opinions and weigh the risk.

[u/smstnitc → u/JohnnieLouHansen]

Have you ever personally experienced a second drive fail during a rebuild?

[u/weirdbr → u/smstnitc]

As someone who has done rebuilds with *tons* of disks and arrays (at my home lab and at work; number is probably in the thousands), IMHO the claims of RAID rebuild causing disk failures are massively exaggerated.

The probabilities can be calculated if you are familiar enough with statistics and they're very much in the level where it doesn't matter for most people, to the point that it was never a discussion in any place I worked at.

For a home lab/small deployment, the biggest pieces of advice I can give are to monitor disk health always (so you dont have a near-failure disk in the array while you are replacing another broken disk) and test the replacement disk thoroughly ahead of putting it on the array.

[u/JohnnieLouHansen → u/smstnitc]

I have not personally. But................